Is tool good and usable for tuning ASM code?
Yes, you can tune ASM code with Intel VTune Amplifier XE. On screenshot below you can see C++ and ASM source view.
Thanks. To clarify, if I only has .ASM source (no .C, .CPP, etc..) I could still open it up and see something simlar with each instruction timed?
Yes, you should be able to see ASM sources.
Event counts will not necessarily be allocated to instructions as you might expect; they may be attributed to subsequent instructions which consume the result of the instruction of interest.